Open a 3-3/8 inch diameter and 2-3/4 inch depth hole, insert the gauge, and secure it in place. Easy installation with 3-wire connection: power, ground, and lighting. This is a complete unit that works directly with a GPS sensor; no additional sensor cables required. Mount the sensor in any position, on or under the dashboard. Takes approximately 30 seconds to acquire signal the first time, and less than 3 seconds subsequently. Performance improves with a clear view of the sky. If signal is lost, reconnect all wires and restart the device. Displays current speed and odometer (non-resettable); no trip meter function. CNSPEED Speedometer features low power consumption, extended lifespan, high precision, fast location confirmation, and short startup time. Speedometer Range: 220 km/h Voltage: 12V/24V Application: Universal Color: As shown Material: ABS + metal Size: 75mm x 90mm x 85mm Package Contents: 1 x 220 km/h Speedometer 1 x Chinese and English Manual 1 x Multi-plug Socket Note: Light shooting and different displays may cause the color of the item in the picture to vary slightly from the actual product. Measurement error allowed is +/- 1-3 cm.